Grid electrode



GRID ELECTRODE Filed Nov. 30, 1937 INVENTOR. 0770 H. .SCHADE' ATTORNEY.

Patented Aug. 29, 1939 UNITED STATES PATENT OFFICE GRID ELECTRODE Otto H. Schade, West CaldwelL N. J., assignor, by

to Radio Corporation of America 'New York, N. Y., a corporation of Delmesne assignments,

aware Application November 30, 1937, Serial No. 177,368

2 Claims.

My invention relates to helically wound grid electrodes and also to improvements in methods of making and in machines for winding such grid electrodes for use in electron discharge tubes and the like.

In some commercial types of electron discharge devices with two or more coaxial helically wound grids, it is desirable to line up the operative portions of the convolutions of the grids between the side rods so that the radial projections of corresponding turns upon the anode be coincident and in registration throughout the length of the rid Wire. This cannot be done with two coaxial flattened helically wound grids of difierent diameters made in the usual way even though the grids are wound with the same turns-per-unit length. Viewed radially of the grids, corresponding turns of the two grids are seen to cross at an acute angle. g

20 An object of my invention is'to make wire wound grid electrodes of diiferent diameters so that the radial projections on the anode of corresponding turns cf two or more coaxial grids be coincident.

Other objects will appear hereinafter.

In making flattened type helical grids with oval, elliptical or rectangular cross section, for example, in accordance with my invention registration of the turns of helically wound grids of different diameters is obtained by decreasing the slope of each flattened half turn of the inner grid to correspond to the slope of the turns of the outer grid. The decrease in slope is secured by making the angle at which the grid wire crosses the side rods steeper than the normal pitch of the grid. The notches in the side rods of the inner grid are cut at an angle steeper than the mean pitch of the inner grid, the ends of the notches in the side rods beginning and terminating at points spaced distance D, Figure 1, longitudinally along the side rods. By winding and peening the grid wire of the inner grid into these angularly cut notches the pitch of each convolution of the inner grid is decreased and brought grinto registry with the corresponding convolutions of the outer grid.

A better understanding of my invention will be obtained by referring to the accompanying drawing in which Figure 1 is an elevation normal to go the plane of the side rods of two mounted grids made according to my invention, Figure 2 is a side elevation of a grid wound in accordance with my invention, Figures 3 and 4 are, respectively, side and top elevations of a grid winding machine made in accordance with my invention,

and Figure 5 is an end view of an elliptical grid ing type with a cathode I, relatively flat or elliptical grids 2 and 3, and plate 4 mounted in the conventional manner upon an insulating spacer 5 carried upon press 6. The outer grid 3 comprisestwo side rods 1 and 8 supporting the convolutions 9 of a helically wound grid wire, the grid wire being welded to or peened into notches uniformly spaced along the side rods. Grid 2 comprises side rods I0 and I I in the plane of the outer grid side rods, wound with grid wire I2, the grid wire being wound with the same turnsper-unit length as the outer grid. The slope of the inner grid wire if Wound in the usual way, as represented by the dotted lines, would be greater than the slope of the outer grid wire even though the two wires are wound with the same pitch, usually designated as turns-per-inch, or TPI.

According to my invention the convolutions of a flat type grid with wire I2 are wound with the same average slope between the side rods as the convolutions of the outer grid wire 9. When notching and peening are used to fasten the grid wire to the side rods, the notches in the side rods of theinner grid are cut at an angle steeper than the mean slope of the inner grid convolutions as best shown in Figure 2, the ends of the notches in the side rods I 0 and I I terminating at points spaced longitudinally along the side rods distance D, Figure 2. Distance D is equal to the distance between the lateral projections on one of the inner grid side rods of the wire of one convolution of the outer grid. By winding and peening the grid wire I2 into these angularly cut notches, the slope of each convolution of the inner grid is decreased and brought into parallel registry with the corresponding con- Volutions of the outer grid. Viewed normal to the plane through the side rods, each turn of the inner grid wire lies behind and substantially parallel to the corresponding convolution of the outer grid.

In the usual grid winding machine the side rods are drawn at a constant speed through a chuck and over a mandrel by a lead screw mechanism geared or driven in synchronism with the mechanism for rotating the chuck and mandrel. As the side rods are successively carried under a notching tool the forward or longitudinal movement of the side rods causes the cutting tool to cut a notch in the side rod at an angle to the side rod proportional to the mean pitch of the grid wire. The usual method of winding grids would, therefore, result in a grid such as grid 2 with grid wire turns of uniform pitch as indicated by dotted lines in Figure 1. I show in Figures 3 and 4 the side and top views, respectively, of an improved grid winding machine for cutting the notches at any desired angle and independent of the 'IPI or pitch of the grid wire. Side rods 59 and H are drawn through rotating chuck l3 and over mandrel M as the rotating mandrel carries the side rods under a cutting tool l5 shown as a sharp edged disc. Grid wire I2 is reeled into the notches made by cutter I5 and carried under peening roller I6. To cut notches in the side rods at an angle greater'than the normal slope of the grid wire, cutting disc I5 is rotatably journalled upon shaft I! held at an angle to the axis of the chuck as shown in top view in Figure 4. Spring l8 biases the cutting wheel against the enlarged end of the shaft IT. As the sharp edge of the cutting wheel enters or digs into the approaching side of the side rod a groove is started which guides the cutter across the side rod at an angle determined by the angle between the plane of the cutter and the chuck axes.

Wound grids with flat sides or grids helically wound upon a mandrel elliptical in cross section, such as mandrel l4 shown in end View in Figure 5, are particularly desirable when constructed in accordance with my invention. The full lines in Figure 5 show side rods IE and H, one above the other and in contact with the cutting and peening wheels l5 and I6. As the mandrel rotates in a counterclockwise direction wire I2 is reeled from a spool on to the mandrel and around the side rods. As the mandrel rotates the side rods are longitudinally drawn at a constant speed advancing the side rods for each degree of rotation. The mandrel may rotate through angle a from the time reeled wire I2 first comes into contact with side rod I!) to the time when the wire leaves contact with side rod N]. This angle of rotation is approximately equal on the particular elliptical grids shown to the angle of rotation 17 necessary to carry the grid wire along the flat side of the ellipse between points of contact on the two side rods. The ad- Vance of the side rods is the same during rotation of the mandrel through angle a as it is during rotation of the mandrel through angle 1), hence for a given number of turns per unit length the slope of the grid wire in the notches must be considerably greater than the slope of the relatively long lengths of grid wire between side rods.

While one specific machine has been described for making my improved helically wound grids, it will be obvious to those skilled in the art that many methods and machines may be used for making my improved grid. It is accordingly desired that my invention be limited only by the prior art and by the appended claims.

I claim:

1. A helically wound grid electrode for an electron discharge device comprising two spaced parallel side rods, a grid wire with spaced turns wound on said side rods, the slope of the grid wire in contact with the side rods being greater than the slope of the turns between the side rods.

2. A grid electrode comprising two spaced parallel side rods, a grid wire helically wound with spaced turns upon said side rods and each turn of the grid wire being attached to and supported by each side rod, the slope of the grid wire in contact with the side rods being greater than the slope of the grid wire between the side rods.

OTTO H. SCHADE 

